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Mahesh

13/01/25 10:21 AM IST

ISRO to attempt ‘docking’ satellites in space

In News
  • Over the next few days, the Indian Space Research Organisation (ISRO) will bring two small satellites closer together and then join them in space, demonstrating “docking” for the first time.
Docking
  • Docking is a process by which two fast-moving spacecraft are brought to the same orbit, and then closer to each other manually or autonomously, and finally joined together.
  • This capability is necessary for carrying out missions that require heavy spacecraft that a single launch vehicle may not be capable of lifting off with.
  • The capability is needed not only for setting up a space station — for which separate modules are joined in space — but also for carrying crew and supplies to it.
Historical background
  • With the space race underway, it was essential for the United States to demonstrate rendezvous (bringing spacecraft close to each other) and docking to achieve the objective of sending humans to the moon.
  • In 1966, the Gemini VIII spacecraft became the first to dock with the Agena target vehicle.
  • It was a crewed mission orbiting the Earth. Interestingly, one of the astronauts on board was Neil Armstrong, who went on to become the first person to set foot on the moon in 1969.
  • While the US mission had astronauts on board to steer the spacecraft, the then Soviet Union in 1967 demonstrated the first uncrewed, automated docking of Kosmos 186 and Kosmos 188 spacecraft.
  • China first demonstrated its docking capability in 2011, when the unmanned Shenzhou 8 spacecraft docked with the Tiangong 1 space laboratory.
  • A year later, it demonstrated the first crewed space docking, when the astronauts manually joined the Shenzhou 9 spacecraft to the same space laboratory.
India's docking mission
  • With its vision of setting up a space station by 2035 and sending humans to the moon by 2040, ISRO has been working on key technologies to realise the vision, such as a new heavy-lift launch vehicle capable of carrying up to 30 tonnes to low earth orbit (an altitude of 2,000 km or less).
  • The missions, however, would require docking capability.
  • Take, for example, the Bharatiya Antariksh Station, which will be built by bringing together five modules in space. The first robotic module is slated to be launched in 2028.
  • Docking capability will also be required for the next lunar mission Chandrayaan-4, which aims to bring back samples from the moon.
  • The planned mission will see the five key modules sent to orbit in two separate launches.
  • The first launch will have four of the five modules, while the propulsion module will carry the rest of the spacecraft from the Earth orbit to the moon orbit.
  • From there, the lander and ascender modules will go to the lunar surface and collect the samples, the ascender module will then hop off with the samples and dock with the transfer module in the lunar orbit.
  • This transfer module will carry back the samples to the earth orbit, where it will dock with a re-entry module that will be launched separately.
  • The module will be designed to withstand the heat of entering the Earth’s atmosphere.
  • In preparation, the space agency already carried out a hop experiment towards the end of the Chandrayaan-3 mission. A human mission to the moon is likely to follow a similar plan.
Docking experiment
  • To demonstrate docking, several manoeuvres will be carried out to progressively bring the SDX01 or Chaser satellite close to the SDX02 or Target satellite.
  • The satellites will drift closer and halt at 5 km, 1.5 km, 500 m, 225 m, 15 m, and 3 m. Finally, the extended rings on both satellites will come in contact and join. The rings will then be retracted and locked in place.
  • Once connected, the satellites will share electrical power.
  • The ISRO scientists will also demonstrate giving commands to both the satellites as one. Once successful, the spacecraft will undock and then drift away to remain in space and conduct experiments for the next two years.
  • Several types of docking mechanisms have been used by the different space agencies over the years, with some allowing interoperability.
  • The International Docking System Standard is used by spacecraft going to the International Space Station.
  • The docking mechanism being used by India is androgynous — meaning the systems on both the Chaser and Target satellites are identical.
  • It is similar to the International Docking System Standard used by other agencies but uses two motors as compared to the 24 used in IDSS.
  • The mission will also use several new sensors such as Laser Range Finder, Rendezvous Sensor, Proximity and Docking sensor to take precise measurements while bringing the two satellites closer and joining them.
  • It will also use a new processor based on satellite navigation systems to determine the relative position and velocity of the other spacecraft.
  • This is a precursor to completely autonomous systems for future missions that would be able to achieve docking without satellite-based navigation data.
Source- Indian Express

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